This invention relates generally to refrigerators and, more particularly, a method and apparatus for controlling refrigeration defrost cycles.
Known frost free refrigerators include a refrigeration defrost system to limit frost buildup on evaporator coils. An electromechanical timer is used to energize a heater after a pre-determined run time of the refrigerator compressor to melt frost buildup on the evaporator coils. To prevent overheating of the freezer compartment during defrost operations when the heater is energized, in at least one type of defrost system the compartment is pre-chilled. After defrost, the compressor is typically run for a predetermined time to lower the evaporator temperature and prevent food spoilage in the refrigerator and/or fresh food compartments of a refrigeration appliance.
Such timer-based defrost systems, however are not as energy efficient as desired. For instance, they tend to operate regardless of whether ice or frost is initially present, and they often pre-chill the freezer compartment regardless of initial compartment temperature. In addition, the defrost heater is typically energized without temperature regulation, and the compressor typically runs after a defrost cycle regardless of the compartment temperature. Such open loop defrost control systems, and the accompanying inefficiencies are undesirable in light of increasing energy efficiency requirements.
While efforts have been made to provide defrost on demand systems employing limited feedback, such as door openings and compressor and evaporator conditions, for improved energy efficiency of defrost cycles, an adaptive defrost on-demand system is desired to alter defrost operation to conserve energy in light of refrigerator operating conditions.
In an exemplary embodiment of the invention, a defrost control system for a self-defrosting refrigerator is configured to monitor compressor load, determine whether at least a first defrost cycle is required based on the compressor load, execute at least one defrost cycle when required; and regulate the defrost cycle to conserve energy.
More specifically a controller is provided for a refrigerator including a compressor, a defrost heater, at least one refrigeration compartment and a temperature sensor thermally coupled to the refrigeration compartment. The controller is operatively coupled to the compressor, the defrost heater, and the temperature sensor, and makes defrost decisions based on temperature conditions in the refrigeration compartment in light of other events, such as refrigerator door openings, completed defrost cycles, and power up events. Defrost cycles are automatically adjusted as operating conditions change, thereby avoiding unnecessary energy consumption that would otherwise occur in a fixed defrost cycle.